Geartrain for a five-speed automatic transmission

ABSTRACT

A geartrain for a five-speed automatic transmission includes first and second compound planetary gear units. The first compound planetary gear unit includes first and second simple planetary gearsets having first, second, third and fourth operating elements. The first operating element acts as an input element. The second compound planetary gear unit includes third and fourth simple planetary gearsets having fifth, sixth, seventh and eighth operating elements. The fifth operating element acts as an output element. The sixth and seventh operating elements are variably connected to the first and second operating elements, respectively. The eighth operating element is fixedly connected to the third operating element. Clutches are provided for variably connecting the sixth and seventh operating elements to the first and second operating elements, respectively. Brakes are provided for selectively connecting the fourth and seventh operating elements to a transmission housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a geartrain, and more particularly, toa geartrain for a five-speed automatic transmission used in vehicles,which can be designed to be compact in size and lightweight by reducingthe number of frictional elements and planetary gearsets.

2. Description of the Related Art

Generally, automatic transmission systems for vehicles comprise atransmission control unit (TCU) which automatically controls shiftratios according to changes in a running condition of the vehicle.

The above-described TCU controls a plurality of friction elementsprovided in a geartrain to either operative or inoperative states toselect one of the three essential elements of the planetary gearset (asun gear, a ring gear, and a planet carrier) to be an input element,another a reaction element, and the last an output element, therebycontrolling the number of output revolutions.

The geartrain is generally designed to realize four forward speeds andone reverse speed. However, with the development of high-power engines,geartrains have been developed to realize five forward speeds and onereverse speed.

The 5-speed geartrain is comprised of three simple planetary gearsetsand at least six friction elements.

However, in such a geartrain for a 5-speed automatic transmission, todrive the vehicle in fourth or fifth speed-overdrive, there is a needfor an element which rotates at a higher speed than that of a finaloutput element. This results in power loss. In addition, the largenumber of friction elements results in a heavy and large-size automatictransmission.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the problemsassociated with the above described conventional geartrain.

It is an object of the present invention to provide a geartrain for afive-speed automatic transmission used in vehicles which, by omitting anelement which rotates at a higher speed than a final output elementneeded in the prior art during overdrive, can minimize power loss.

It is another object of the present invention to provide a geartrain fora five-speed automatic transmission which can be designed to be compactin size and lightweight by reducing the number of friction elements.

According to a feature of the present invention, a geartrain for afive-speed automatic transmission comprises a first compound planetarygear unit comprising first and second simple planetary gearsets havingfirst, second, third and fourth operating elements, said first operatingelement acting as an input element; a second compound planetary gearunit comprising third and fourth simple planetary gearsets having fifth,sixth, seventh and eighth operating elements, said fifth operatingelement acting as an output element, said sixth and seventh operatingelements being variably connected to said first and second operatingelements, respectively, and said eighth operating element being fixedlyconnected to the third operating element; clutch means for variablyconnecting said sixth and seventh operating elements to said first andsecond operating elements, respectively; and brake means for selectivelyconnecting the fourth and seventh operating elements to a transmissionhousing.

According to a first embodiment of the present invention, each of saidfirst and second simple planetary gearsets is a single pinion planetarygearset.

In the first embodiment, the first operating element is a sun gear ofthe first simple planetary gearset; the second operating element is aring gear of the second simple planetary gearset; the third operatingelement is a combination of a planet carrier of the first simpleplanetary gearset and a planet carrier of the second simple planetarygearset; and the fourth operating element is a combination of a ringgear of the first simple planetary gearset and a sun gear of the secondsimple planetary gearset.

In the first embodiment, the third simple planetary gearset is a doublepinion planetary gearset, and the fourth simple planetary gearset is asingle pinion planetary gearset.

In the first embodiment, the fifth operating element is a combination ofa sun gear of the third simple planetary gearset and a ring gear of thefourth simple planetary gearset; the sixth operating element is a planetcarrier of the fourth simple planetary gearset; the seventh operatingelement is a ring gear of the third simple planetary gearset; and theeighth operating element is a combination of a planet carrier of thethird simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.

In the first embodiment, the clutch means comprises a first clutchinterposed between the ring gear of the second simple planetary gearsetand the ring gear of the third simple planetary gearset and a secondclutch interposed between the sun gear of the first simple planetarygearset and the planet carrier of the fourth simple planetary gearset.

In the first embodiment, the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing and a second brake interposed between thecombination of the ring gear of the first simple planetary gearset andthe sun gear of the second simple planetary gearset and the transmissionhousing.

According to second embodiment of the present invention, the firstsimple planetary gearset is a double pinion planetary gearset, and thesecond simple planetary gearset is a single pinion planetary gearset.

In the second embodiment, the first operating element is a sun gear ofthe first simple planetary gearset; the second operating element is acombination of a ring gear of the first simple planetary gearset and aring gear of the second simple planetary gearset; the third operatingelement is a planet carrier of the second simple planetary gearset; andthe fourth operating element is a combination of a planet carrier of thefirst simple planetary gearset and a sun gear of the second simpleplanetary gearset.

In the second embodiment, the third simple planetary gearset is a doublepinion planetary gearset and the fourth simple planetary gearset is asingle pinion planetary gearset.

In the second embodiment, the fifth operating element is a combinationof a sun gear of the third simple planetary gearset and a ring gear ofthe fourth simple planetary gearset; the sixth operating element is aplanet carrier of the fourth simple planetary gearset; the seventhoperating element is a ring gear of the third simple planetary gearset;and the eighth operating element is a combination of a planet carrier ofthe third simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.

In the second embodiment, the clutch means comprises a first clutchinterposed between the combination of the ring gear of the first simpleplanetary gearset and the ring gear of the second simple planetarygearset and the ring gear of the third simple planetary gearset, and asecond clutch interposed between the sun gear of the first simpleplanetary gearset and the planet carrier of the fourth simple planetarygearset.

In the second embodiment, the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing and a second brake interposed between thecombination of the planet carrier of the first simple planetary gearsetand the sun gear of the second simple planetary gearset and thetransmission housing.

According to a third embodiment of the present invention, the firstoperating element is a sun gear of the second simple planetary gearset;the second operating element is a planet carrier of the first simpleplanetary gearset; the third operating element is a combination of aring gear of the first simple planetary gearset and a planet carrier ofthe second simple planetary gearset; and the fourth operating element isa combination of a sun gear of the first simple planetary gearset and aring gear of the second simple planetary gearset.

In the third embodiment, the third simple planetary gearset is a doublepinion planetary gearset and the fourth simple planetary gearset is asingle pinion planetary gearset.

In the third embodiment, the fifth operating element is a combination ofa sun gear of the third simple planetary gearset and a ring gear of thefourth simple planetary gearset; the sixth operating element is a planetcarrier of the fourth simple planetary gearset; the seventh operatingelement is a ring gear of the third simple planetary gearset; and theeighth operating element is a combination of a planet carrier of thethird simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.

In the third embodiment, the clutch means comprises a first clutchinterposed between the planet carrier of the first simple planetarygearset and the ring gear of the third simple planetary gearset, and asecond clutch interposed between the sun gear of the second simpleplanetary gearset and the planet carrier of the fourth simple planetarygearset.

In the third embodiment, the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing, and a second brake interposed between thecombination of the sun gear of the first simple planetary gearset andthe ring gear of the second simple planetary gearset and thetransmission housing.

According to a fourth embodiment of the present invention, the firstoperating element is a combination of a sun gear of the first simpleplanetary gearset and a sun gear of the second simple planetary gearset;the second operating element is a ring gear of the first simpleplanetary gearset; the third operating element is a planet carrier ofthe second simple planetary gearset; and the fourth operating element isa combination of a planet carrier of the first simple planetary gearsetand a ring gear of the second simple planetary gearset.

In the fourth embodiment, the third simple planetary gearset is a doublepinion planetary gearset and the fourth simple planetary gearset is asingle pinion planetary gearset.

In the fourth embodiment, the fifth operating element is a combinationof a sun gear of the third simple planetary gearset and a ring gear ofthe fourth simple planetary gearset; the sixth operating element is aplanet carrier of the fourth simple planetary gearset; the seventhoperating element is a ring gear of the third simple planetary gearset;and the eighth operating element is a combination of a planet carrier ofthe third simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.

In the fourth embodiment, the clutch means comprises a first clutchinterposed between the ring gear of the first simple planetary gearsetand the ring gear of the third simple planetary gearset, and a secondclutch interposed between the combination of the sun gear of the firstsimple planetary gearset and the sun gear of the second simple planetarygearset and the planet carrier of the fourth simple planetary gearset.

In the fourth embodiment, the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing, and a second brake interposed between thecombination of the planet carrier of the third simple planetary gearsetand the ring gear of the second simple planetary gearset and thetransmission housing.

According to a fifth embodiment of the present invention, each of thefirst and second simple planetary gearsets is a double pinion planetarygearset.

In the fifth embodiment, the first operating element is a sun gear ofthe first simple planetary gearset; the second operating element is acombination of a ring gear of the first simple planetary gearset and aplanet carrier of the second simple planetary gearset; the thirdoperating element is a ring gear of the second simple planetary gearset;and the fourth operating element is a combination of a planet carrier ofthe first simple planetary gearset and a sun gear of the second simpleplanetary gearset.

In the fifth embodiment, the third simple planetary gearset is a doublepinion planetary gearset and the fourth simple planetary gearset is asingle pinion planetary gearset.

In the fifth embodiment, the fifth operating element is a combination ofa sun gear of the third simple planetary gearset and a ring gear of thefourth simple planetary gearset; the sixth operating element is a planetcarrier of the fourth simple planetary gearset; the seventh operatingelement is a ring gear of the third simple planetary gearset; and theeighth operating element is a combination of a planet carrier of thethird simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.

In the fifth embodiment, the clutch means comprises a first clutchinterposed between the combination of the ring gear of the first simpleplanetary gearset and the planet carrier of the second simple planetarygearset and the ring gear of the third simple planetary gearset, and asecond clutch interposed between the sun gear of the first simpleplanetary gearset and the planet carrier of the fourth simple planetarygearset.

In the fifth embodiment, the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing, and a second brake interposed between thecombination of the planet carrier of the first simple planetary gearsetand the sun gear of the second simple planetary gearset and thetransmission housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate an embodiment of the invention,and, together with the description, serve to explain the principles ofthe invention:

FIG. 1 is a schematic diagram illustrating a geartrain according to afirst embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a geartrain according to asecond embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a geartrain according to athird embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a geartrain according to afourth embodiment of the present invention;

FIG. 5 is a schematic diagram illustrating a geartrain according to afifth embodiment of the present invention;

FIG. 6 is a lever analogy representation which can be obtained throughgeartrains according to various embodiments of the present inventiondepicted in FIGS. 1-5;

FIG. 7 is a schematic diagram illustrating an operation of forwardfirst, second and third speeds of a geartrain according to a preferredembodiment of the present invention through a lever analogy;

FIG. 8 is a schematic diagram illustrating an operation of forwardfourth and fifth speeds of a geartrain according to a preferredembodiment of the present invention through a lever analogy diagram;

FIG. 9 is a schematic diagram illustrating an operation of reverse speedof a geartrain according to a preferred embodiment of the presentinvention through a lever analogy diagram; and

FIG. 10 is a chart illustrating the operation of friction elements ineach shift range of a power train according to a preferred embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

First Embodiment

Referring first to FIG. 1, there is shown a schematic diagram of ageartrain according to a first embodiment of the present invention.

The geartrain of this embodiment comprises an engine 100 for generatingpower, a torque converter T for multiplying torque generated from theengine 100, and first and second compound planetary gear units 1 and 3for receiving converted torque through an input shaft 10 and foroutputting five forward speeds and one reverse speed to a transfer drivegear TD.

The first compound planetary gear unit 1 comprises first and secondsimple planetary gearsets PG1 and PG2 each of which is a single pinionplanetary gearset.

In the first compound planetary gear unit 1, a ring gear R1 of the firstsimple planetary gearset PG1 is fixedly connected to a sun gear S2 ofthe second simple planetary gearset PG2, and a planet carrier Ca1,connecting pinion gears P1 to each other, of the first simple planetarygearset PG1 is fixedly connected to a planet carrier Ca2, connectingpinion gears P2 to each other, of the second simple planetary gearsetPG2.

Therefore, the first compound planetary gear unit 1 consists of fouroperating elements, i.e., a sun gear S1 of the first simple planetarygearset PG1, a ring gear R2 of the second simple planetary gearset PG2,a combination of the ring gear R1 and sun gear S2 of the first andsecond simple planetary gearsets PG1 and PG2, and a combination of theplanet carriers Ca1 and Ca2 of the first and second simple planetarygearsets PG1 and PG2.

The sun gear S1 is fixedly mounted around the input shaft 10 to act asan input element. The combination of the ring gear R1 and sun gear S2 isvariably connected to a transmission housing 20 to selectively act as areacting element.

The second compound planetary gear unit 3 comprises a third simpleplanetary gearset PG3 which is a double pinion planetary gearset and afourth simple planetary gearset PG4 which is a single pinion planetarygearset.

In the second compound planetary gear unit 3, a sun gear S3 of the thirdsimple planetary gearset PG3 is fixedly connected to a ring gear R4 ofthe fourth simple planetary gearset PG4, and a planet carrier Ca3,connecting pinion gears P3 to each other, of the third simple planetarygearset PG3 is fixedly connected to a sun gear S4 of the fourth simpleplanetary gearset PG4.

Therefore, the second compound planetary gear unit 3 consists of fouroperating elements, i.e., a ring gear R3 of the third simple planetarygearset PG3, a planet carrier Ca4 of the fourth simple planetary gearsetPG4, a combination of the sun gear S3 and ring gear R4, and acombination of the planet carrier Ca3 and the sun gear S4.

The ring gear R3 of the third simple planetary gearset PG3 is variablyconnected to the transmission housing 20 to selectively act as areacting element. The combination of the sun gear S3 and ring gear R4 ofthe third and fourth simple planetary gearsets PG3 and PG4 is connectedto the transfer drive gear TD to act as an output element.

The above described first and second compound planetary gear units 1 and3 are combined to each other. That is, the ring gear R2 of the secondsimple planetary gearset PG2 is variably connected to the ring gear R3of the third simple planetary gearset PG3; the sun gear S1 of the firstsimple planetary gearset PG1 is variably connected to the planet carrierCa4 of the fourth simple planetary gearset PG4; and the combination ofthe planet carriers Ca1 and Ca2 of the first and second simple planetarygearsets PG1 and PG2 is fixedly connected to the combination of theplanet carrier Ca3 and sun gear S4 of the third and fourth simpleplanetary gearsets PG3 and PG4.

A first clutch C1 is interposed between the ring gears R2 and R3 of thesecond and third simple planetary gearsets PG2 and PG3. The first clutchC1 is operated in forward first, second and third speeds to connect thering gear R2 to the ring gear R3. A second clutch C2 is interposedbetween the sun gear S1 of the first simple planetary gearset PG1 andthe planet carrier Ca4 of the fourth simple planetary gearset PG4. Thesecond clutch C2 is operated in forward third, fourth and fifth speedsto connect the sun gear S1 to the planet carrier Ca4.

In addition, a first brake B1 is interposed between the ring gear R3 ofthe third simple planetary gearset PG3 and the transmission housing 20.The first brake B1 is engaged to fix the ring gear R3 in forward firstand fifth speeds and reverse speed. A second brake B2 is interposedbetween the combination of the ring gear R1 and sun gear S2 of the firstand second simple planetary gearsets PG1 and PG2 and the transmissionhousing 20, such that it can operate in the forward second and fourthspeeds and the reverse speed to fix the combination of the ring gear R1and sun gear S2.

The above described geartrain can be illustrated as a leverrepresentation as shown in FIG. 6. In FIG. 6, levers L1 and L2 indicatethe first and second compound planetary gear units 1 and 3,respectively. The four operating elements of the first compoundplanetary gear units 1 are indicated as first, second, third and fourthoperating elements A, D, E and F on the first lever L1, and the fouroperating elements of the second compound planetary gear unit 3 areindicated as first, second, third and fourth operating elements G, H, Iand J on the second lever L2.

Describing the first lever L1 more in detail, the first operatingelement A indicates the sun gear S1 of the first simple planetarygearset PG1, the second operating element D indicates the ring gear R2of the second simple planetary gearset PG2, the third operating elementE indicates the combination of the planet carriers Ca1 and Ca2 of thefirst and second simple planetary gearsets PG1 and PG2, and the fourthoperating element F indicates the combination of the ring gear R1 andsun gear S2 of the first and second simple planetary gearsets PG1 andPG2.

In addition, in the second lever L2, the first operating element Gindicates the combination of the sun gear S3 and ring gear R4 of thethird and fourth simple planetary gearsets PG3 and PG4, and the secondoperating element H indicates the planet carrier Ca4 of the fourthsimple planetary gearset PG4. The third operating element I indicatesthe ring gear R3 of the third simple planetary gearset PG3, and thefourth operating element J indicates the combination of the planetcarrier Ca3 and sun gear S4 of the third and fourth simple planetarygearsets PG3 and PG4.

In the first lever L1, as described above, the first operating element Ais fixed on the input shaft 10 to act as an input element, and thefourth operating element F is variably connected to the transmissionhousing 20 by the second brake B2 to selectively act as a reactingelement.

In the second lever L2, the first operating element G is connected tothe transfer drive gear TD to act as an output element, and the thirdoperating element I is variably connected to the transmission housing 20by the first brake B1 to selectively act as a reacting element.

The first clutch C1 is interposed between the second operating element Dof the first lever L1 and the third operating element I of the secondlever L2 to selectively interconnect the operating elements D and I. Thesecond clutch C2 is interposed between the first operating element A ofthe first lever L1 and the second operating element H of the secondlever L2 to interconnect the operating elements A and H.

In the forward first, second and third speeds D1, D2 and D3, since thefirst clutch C1 is operated as charted in FIG. 10, the leverrepresentation of FIG. 6 can be illustrated as a single third lever L3having first, second, third, fourth, fifth and sixth nodes N1, N2, N3,N4, N5 and N6 as shown in FIG. 7.

That is, in the third lever L3, the first node N1 indicates the firstoperating element A of the first compound planetary gear unit 1, thesecond node N2 indicates the first operating element G of the secondcompound planetary gear unit 3, the third node N3 indicates the secondoperating element H of the second compound planetary gear unit 3, thefourth node N4 indicates a combination of the second operating element Dof the first compound planetary gear unit 1 and the third operatingelement I of the second compound planetary gear unit 3, the fifth nodeN5 indicates the combination of the third operating elements E of thefirst compound planetary gear unit 1 and the fourth operating elements Jof the second compound planetary gear unit 3, and the sixth node N6indicates the fourth operating element F of the first compound planetarygear unit 1.

That is, the first node N1 indicates the combination of the sun gear S1of the first simple planetary gearset PG1, the second node N2 indicatesthe combination of the sun gear S3 and ring gear R4 of the third andfourth simple planetary gearsets PG3 and PG4, the third node N3indicates the planet carrier Ca4 of the fourth simple planetary gearsetPG4, the fourth node N4 indicates the combination of the ring gears R2and R3 of the second and third simple planetary gearsets PG2 and PG3,the fifth node N5 indicates the combination of the planet carriers Ca1,Ca2 and Ca3 and sun gear S4 of the fist, second, third and fourth simpleplanetary gearsets PG1, PG2, PG3 and PG4, and the sixth node N6indicates the ring gear R1 and sun gear S2 of the first and secondsimple planetary gearsets PG1 and PG2.

Through this lever analogy, shift ratios of the forward first, secondand third speeds can be demonstrated.

FORWARD FIRST SPEED

In the forward first speed D1, the first clutch C1 and the first brakeB1 are operated as charted in FIG. 10. Accordingly, the first node N1indicating the first operating element A of the first lever L1 becomesthe input element, and the fourth node N4 indicating the combination ofthe second operating element D of the first lever L1 and the thirdoperating element I of the second lever L2 becomes a reacting element.Accordingly, the first forward speed is outputted through the secondnode N2 indicating the first operating element G of the At second leverL2.

Namely, the sun gear S1 of the first simple planetary gearset PG1becomes the input element, and the combination of the sun gear S3 andring gear R4 of the third and fourth simple planetary gearsets PG3 andPG4 becomes the output element.

Therefore, when assuming that the output revolution number of thecombination of the sun gear S3 and ring gear R4 is "1", a lineconnecting the output point of the second node N2, acting as the outputelement, to the fourth node N4, acting as the reacting element, becomesthe first speed line 11. At this point, the number of input revolutionD1 of the first node N1 becomes the first input speed which is higherthan the output speed "1". This shows that speed reduction is realized.

In the first speed state, the element of the third node N3 rotates inthe output direction at a number of revolutions less than that of theoutput, while the elements in the fifth and sixth nodes N5 and N6 rotatein the opposite direction of the output.

FORWARD SECOND SPEED

If throttle opening is increased in the forward first speed state, thefirst brake B1 is disengaged, while the second brake B2 is operated ascharted in FIG. 10. Accordingly, the reacting element is changed fromthe fourth node N4 to the sixth node N6 indicating the fourth operatingelements F of the first lever L1.

Namely, the sun gear S1 of the first simple planetary gearset PG1becomes the input element, and the combination of the ring gear R1 andsun gear S2 of the first and second simple planetary gearsets PG1 andPG2 becomes the reacting element. The combination of the sun gear S3 andring gear R4 of the third and fourth simple planetary gearsets PG3 andPG4 becomes the output element.

That is, when the output revolution number of the combination of the sungear S3 and ring gear R4 is assumed to be "1", a line connecting theoutput speed point of the second node N2, acting as an output element,to the sixth node N6, acting as the reacting element, becomes the secondspeed line 12. At this point, the number of input revolution D2 of thefirst node N1 becomes the second input speed which is higher than theoutput speed "1". This shows that speed reduction is realized.

In this forward second speed state, all operating elements of the third,fourth and fifth nodes N3, N4 and N5 rotate in the output direction at anumber of revolutions less than that of the output.

FORWARD THIRD SPEED

If the throttle opening is increased in the forward second speed state,the second brake B2 is released, while the second clutch C2 is operatedas charted in FIG. 12. Accordingly, since the first and second compoundplanetary gear units 1 and 3 are locked as the input is realized throughthe first node N1, the forward third speed is outputted through thesecond node N2 indicating the first operating element G of the secondlever L2.

That is, in a state where the input is realized through first node N1,since the first and second compound planetary gear units 1 and 3 arelocked, the third speed is outputted through the transfer drive gear TDfixed to the second node N2 indicating the combination of the sun gearS3 and ring gear R4 of the third and fourth simple planetary gearsetsPG3 and PG4.

That is, when assuming that the output revolution number of thecombination of the sun gear S3 and ring gear R4 is "1", a lineconnecting the output speed point of the second node N2 to the equallevel of the first node N1, acting as the input element, becomes thethird speed line 13. At this point, the number of input revolution ofthe first node N1 becomes the third input speed D3 which is equal tothat of the output speed "1". This shows that neither speed reductionnor speed increase occurs.

In this forward third speed state, all operating elements of the nodesN1 through N6 rotate in the output direction at the same number ofrevolutions as that of the output.

Forward Fourth and Fifth Speeds!

In the forward fourth and fifth speeds, since the second clutch C2 isoperated as charted in FIG. 10, the first and second levers L1 and L2 ofFIG. 6 can be illustrated as a single fourth lever L4 having firstthrough sixth nodes N1, N2, N3, N4, N5 and N6 as shown in FIG. 8.

That is, in the fourth lever L4, the first node N1 indicates the firstoperating element G of the second compound planetary gear unit 3, thesecond node N2 indicates a combination of the first operating element Aof the first compound planetary gear unit 1 and the second operatingelement H of the second compound planetary gear unit 3, the third nodeN3 indicates the third operating element I of the second compoundplanetary gear unit 3, the fourth node N4 indicates the third operatingelement D of the first compound planetary gear unit 1, the fifth node N5indicates the combination of the third operating element E of the firstcompound planetary gear unit 1 and the fourth operating element J of thesecond compound planetary gear unit 3, and the sixth node N6 denotes thefourth operating element f of the first compound planetary gear unit 1.

That is, the first node N1 indicates the combination of the sun gear S3and ring gear R4 of the third and fourth simple planetary gearsets PG3and PG4, the second node N2 indicates the combination of the sun gear S1and planet carrier Ca4 of the first and fourth simple planetary gearsetsPG1 and PG4, the third node N3 indicates the ring gear R3 of the thirdsimple planetary gearset PG3, the fourth node N4 indicates the ring gearR2 of the second simple planetary gearset PG2, the fifth node N5indicates the combination of the planet carriers Ca1, Ca2 and Ca3 andsun gear S4 of the first, second, third and fourth simple planetarygearsets PG1, PG2, PG3 and PG4, and the sixth node N6 indicates thecombination of the ring gear R1 and sun gear S2 of the first and secondsimple planetary gearsets PG1 and PG2.

Through this lever analogy, shift ratios of the forward fourth and fifthspeeds can be demonstrated.

FORWARD FOURTH SPEED

If the throttle opening is increased in the third speed state, the firstclutch C1 is disengaged, while the second brake B2 is operated ascharted in FIG. 10. Accordingly, the second node N2 indicating thecombination of the first operating element A of the first compoundplanetary gear unit 1 and the second operating element H of the secondcompound planetary gear unit 3 becomes an input element, while the sixthnode N6 indicating the fourth operating element F of the first compoundplanetary gear unit 1 becomes a reacting element. Therefore, the forwardfourth speed is outputted through the first node N1 indicating the firstoperating element G of the second compound planetary gear unit 3.

Namely, the input element becomes the combination of the sun gear S1 andplanet carrier Ca4 of the first and fourth simple planetary gearsets PG1and PG4, and the reacting element becomes the combination of the ringgear R1 and sun gear S2 of the first and second simple planetarygearsets PG1 and PG2. Accordingly, the forward fourth speed is outputedthrough the transfer drive gear TD fixed to the first node N1 indicatingthe combination of the sun gear S3 and the ring gear R4 of the third andfourth simple planetary gearsets PG3 and PG4.

That is, when assuming that the output revolution number of thecombination of the sun gear S3 and ring gear R4 is "1", a lineconnecting the output speed point of the first node N1 to the sixth nodeN6, acting as the reacting element, becomes a fourth speed line 14. Atthis point, the number of input revolution D4 of the second node N2becomes the fourth input speed which is less than the output speed "1".This shows that speed increase is realized. That is, the fourth speedstate is an overdrive in which output speed is higher than the inputspeed.

In the fourth speed state, all the operating elements of the third,fourth and fifth nodes N3, N4 and N5 rotate in the output direction at anumber of revolutions less than that of the output. Therefore, sincethere is no operating element which rotates at a number of revolutionshigher than that of output, power loss is prevented.

FORWARD FIFTH SPEED

If the throttle opening is increased in the fourth speed state, thesecond brake B2 is disengaged, while the first brake B1 is engaged.Accordingly, the second node N2 becomes the input element, while thethird node N3 indicating the third operating element I of the secondlever L2 becomes the reacting element. In addition, the first node N1indicating the first operating element G of the second lever L2 becomesthe output element.

That is, the input element becomes a combination of the sun gear S1 andplanet carrier Ca4 of the first and fourth simple planetary gearsets PG1and PG4. The reacting element becomes the third node N3 indicating thering gear R3 of the third simple planetary gearset PG3. Therefore, theforward fifth speed is outputted through the transfer drive gear TDfixed to the first node N1 indicating the combination of the sun gear S3and ring gear R4 of the third and fourth simple planetary gearsets PG3and PG4.

That is, when the output revolution number of the combination of the sungear S3 and ring gear R4 is assumed to be "1", a line connecting theoutput speed point of the first node N1 to the third node N3, acting asthe reacting element, becomes a fifth speed line 15. At this point, thenumber of input revolution D5 of the second node N2 becomes the fifthinput speed which is less than the output speed "1". This shows thatspeed increase is realized. That is, the fifth speed state is anoverdrive state in which the output speed is higher than the inputspeed.

In the fifth speed state, the operating elements of the fourth, fifthand sixth nodes N4, N5 and N6 rotate in the opposite direction of theoutput direction. Therefore, since the third node N3 is fixed, that is,there is no operating element which idles at the number of revolutionshigher than that of output, power loss is prevented.

REVERSE SPEED

When a shift mode is selected in a reverse mode, the first and secondclutches C1 and C2 are disengaged, and the first and second brakes B1and B2 are operated.

Accordingly, in the reverse mode, the first and second levers L1 and L2can be illustrated as a single lever L5 having first through sixth nodesN1 through N6 as shown in FIG. 9.

That is, in the fifth lever L5, the first node N1 indicates the firstoperating element G of the second compound planetary gear unit 3, thesecond node N2 indicates the second operating element H of the secondcompound planetary gear unit 3, the third node N3 indicates acombination of the fourth operating element of the first compoundplanetary gear unit 1 and the third operating element I of the secondcompound planetary gear unit 3, the fourth node N4 indicates acombination of the third operating elements E of the first compoundplanetary gear unit 1 and the fourth operating element of the secondcompound planetary gear unit 3, the fifth node N5 denotes the secondoperating elements D of the first compound planetary gear unit 1, andthe sixth node N6 indicates the first operating element A of the firstcompound planetary gear unit 1.

That is, the first node N1 indicates the combination of the sun gear S3and ring gear R4 of the third and fourth simple planetary gearsets PG3and PG4, the second node N2 indicates the planet carrier Ca4 of thefourth simple planetary gearset PG4, the third node N3 indicates thecombination of the ring gear R1, sun gear S2 and ring gear R3 of thefirst, second and third simple planetary gearsets PG1, PG2 and PG3, thefourth node N4 indicates a combination of the planet carriers Ca1, Ca2and Ca3 and sun gear S4 of the first, second, third and fourth simpleplanetary gearsets PG1, PG2, PG3 and PG4, the fifth node N5 indicatesthe ring gear R2 of the second simple planetary gearset PG2, and thesixth node N6 indicates the sun gear S1 of the first simple planetarygearset PG1.

Through this lever analogy, the reverse speed can be demonstrated.

In the reverse mode, the first and second clutches C1 and C2 aredisengaged, while the first and second brakes B1 and B2 are operated.Accordingly, the sixth node N6 indicating the first operating element Aof the first compound planetary gear unit 1 becomes the input element,while both the fourth operating element F of the first compoundplanetary gear unit 1 and the third I of the second compound planetarygear unit 3 becomes the reacting elements. In addition, the first nodeN1 indicating the first operating element G of the second compoundplanetary gear unit 3 becomes the output element.

That is, the combination of the sun gear S1 of the first simpleplanetary gearset PG1 becomes the input element, while both combinationof the ring gear R1, sun gear S2 and ring gear R3 of the first, secondand third simple planetary gearsets PG1, PG2 and PG3 acts as a reactingelement. Therefore, the reverse speed is outputted through the transferdrive gear TD fixed to the first node N1 indicating the combination ofthe sun gear S3 and ring gear R4 of the third and fourth simpleplanetary gearsets PG3 and PG4.

That is, when assuming that the output revolution number of thecombination of the sun gear S3 and ring gear R4 is "1", a lineconnecting the output speed point of the first node N1, acting as anoutput element, to the third node N3, acting as the reacting element,becomes the reverse speed line 16. At this point, the number of inputrevolution REV of the sixth node N6 becomes the reverse input speed.That is, the direction of the input speed is opposite to the outputspeed.

Second Embodiment

Referring to FIG. 2, there is shown a schematic diagram of a geartrainaccording to a second embodiment of the present invention.

The geartrain of this embodiment comprises an engine 100 for generatingpower, a torque converter T for multiplying torque generated from theengine 100, and first and second compound planetary gear units 1 and 3for receiving converted torque through an input shaft 10 and foroutputting five forward speeds and one reverse speed to a transfer drivegear TD.

In this embodiment, the first compound planetary gear unit 1 comprises afirst simple planetary gearset PG1 which is a double pinion planetarygearset and a second simple planetary gearset PG2 which is a singlepinion planetary gearset. The second compound planetary gear unit 3comprises a third simple planetary gearset PG3 which is a double pinionplanetary gearset and a fourth simple planetary gearset PG4 which is asingle pinion planetary gearset.

In the first compound planetary gear unit 1, a ring gear R1 of the firstsimple planetary gearset PG1 is fixedly connected a ring gear R2 of thesecond simple planetary gearset PG2, and a planet carrier Ca1 of thefirst simple planetary gearset PG1 is connected to a sun gear S2 of thesecond simple planetary gearset PG2.

Therefore, the first compound planetary gear unit 1 consists of fouroperating elements, i.e., a sun gear S1 of the first simple planetarygearset PG1, a planet carrier Ca2 of the second simple planetary gearsetPG2, a combination of the ring gears R1 and R2 of the first and secondsimple planetary gearsets PG1 and PG2, and a combination of the planetcarrier Ca1 and sun gear S2 of the first and second simple planetarygearsets PG1 and PG2.

Since the structure of the second compound planetary gear unit 3 is thesame as that of the first embodiment, a detailed description thereofwill be omitted and incorporated herein as a reference.

The above described first and second compound planetary gear units 1 and3 are combined to each other. That is, the planet carrier Ca2 of thesecond simple planetary gearset PG2 is fixedly connected to thecombination of the planet carrier Ca3 and sun gear S4 of the third andfourth simple planetary gearsets PG3 and PG4; the combination of thering gears R1 and R2 of the first and second simple planetary gearsetsPG1 and PG2 is variably connected to the ring gear R3 of the thirdsimple planetary gearset PG3; and the sun gear S1 of the first simpleplanetary gearset PG1 is variably connected to the planet carrier Ca4 ofthe fourth simple planetary gearset PG4. In addition, the combination ofthe sun gear S3 and ring gear R4 of the third and fourth simpleplanetary gearsets PG3 and PG4 is fixed to the transfer drive gear TD.

A first clutch C1 is interposed between the combination of the ringgears R1 and R2 of the first and second simple planetary gearsets PG1and PG2 and the ring gear R3 of the third simple planetary gearset PG3.The first clutch C1 is operated in forward first, second and thirdspeeds to connect the combination of the ring gears R1 and R2 of thefirst and second simple planetary gearsets PG1 and PG2 to the ring gearR3 of the third simple planetary gearset PG3. A second clutch C2 isinterposed between the sun gear S1 of the first simple planetary gearsetPG1 and the planet carrier Ca4 of the fourth simple planetary gearsetPG4. The second clutch C2 is operated in forward third, fourth and fifthspeeds to connect the sun gear S1 to the planet carrier Ca4.

In addition, a first brake B1 is interposed between the ring gear R3 ofthe third simple planetary gearset PG3 and the transmission housing 20.The first brake B1 is engaged to fix the ring gear R3 in forward firstand fifth speeds and reverse speed. A second brake B2 is interposedbetween the combination of the planet carrier Ca1 and sun gear S2 of thefirst and second simple planetary gearsets PG1 and PG2 and thetransmission housing 20, such that it can operate in the forward secondand fourth speeds and the reverse speed to fix the combination of theplanet carrier Ca1 and sun gear S1.

The above described geartrain can be illustrated as a leverrepresentation as shown in FIG. 6. In FIG. 6, levers L1 and L2 indicatethe first and second compound planetary gear units 1 and 3,respectively. The four operating elements of the first compoundplanetary gear units 1 are indicated as first, second, third and fourthoperating elements A, D, E and F on the first lever L1, and the fouroperating elements of the second compound planetary gear unit 3 areindicated as first, second, third and fourth operating elements G, H, Iand J on the second lever L2.

In the first lever L1, the first operating element A indicates the sungear S1 of the first simple planetary gearset PG1, the second operatingelement D indicates the combination of the ring gears R1 and R2 of thefirst and second simple planetary gearsets PG1 and PG2, the thirdoperating element E indicates the planet carrier Ca2 of the secondsimple planetary gearset PG2, and the fourth operating element Findicates the combination of the planet carrier Ca1 and sun gear S2 ofthe first and second simple planetary gearsets PG1 and PG2.

Since the operating elements of the second lever L2 are the same asthose of the first embodiment, a detailed description thereof will beomitted and incorporated herein as a reference.

The detailed description of shift ratios through the lever analogy willbe omitted herein as the shift ratios are the same as those of the firstembodiment.

Third Embodiment

Referring to FIG. 3, there is shown a schematic diagram of a geartrainaccording to a third embodiment of the present invention.

The geartrain of this embodiment comprises an engine 100 for generatingpower, a torque converter T for multiplying torque generated from theengine 100, and first and second compound planetary gear units 1 and 3for receiving converted torque through an input shaft 10 and foroutputting five forward speeds and one reverse speed to a transfer drivegear TD.

In this embodiment, the first compound planetary gear unit 1 comprises afirst simple planetary gearset PG1 which is a double pinion planetarygearset and a second simple planetary gearset PG2 which is a singlepinion planetary gearset. The second compound planetary gear unit 3comprises a third simple planetary gearset PG3 which is a double pinionplanetary gearset and a fourth simple planetary gearset PG4 which is asingle pinion planetary gearset.

In the first compound planetary gear unit 1, a ring gear R1 of the firstsimple planetary gearset PG1 is fixedly connected a planet carrier Ca2of the second simple planetary gearset PG2, and a sun gear S1 of thefirst simple planetary gearset PG1 is connected to a ring gear R2 of thesecond simple planetary gearset PG2.

Therefore, the first compound planetary gear unit 1 consists of fouroperating elements, i.e., a planet carrier Ca1 of the first simpleplanetary gearset PG1, a sun gear S2 of the second simple planetarygearset PG2, a combination of the ring gear R1 and planet carrier Ca2 ofthe first and second simple planetary gearsets PG1 and PG2, and acombination of the sun gear S1 and ring gear R2 of the first and secondsimple planetary gearsets PG1 and PG2.

Since the structure of the second compound planetary gear unit 3 is thesame as that of the first embodiment, a detailed description thereofwill be omitted and incorporated herein as a reference.

The above described first and second compound planetary gear units 1 and3 are combined to each other. That is, the combination of the ring gearR1 and planet carrier Ca2 of the first and second simple planetarygearsets PG1 and PG2 is fixedly connected to the combination of theplanet carrier Ca3 and sun gear S4 of the third and fourth simpleplanetary gearsets PG3 and PG4; the planet carrier Ca1 of the firstsimple planetary gearset PG1 is variably connected to the ring gear R3of the third simple planetary gearset PG3; and the sun gear S2 of thesecond simple planetary gearset PG2 is variably connected to the planetcarrier Ca4 of the fourth simple planetary gearset PG4. In addition, thecombination of the sun gear S3 and ring gear R4 of the third and fourthsimple planetary gearsets PG3 and PG4 is fixed to the transfer drivegear TD. The sun gear S2 of the second simple planetary gearset PG2 isfixed around the input shaft 10 so as to act as an input element.

A first clutch C1 is interposed between the planet carrier Ca1 of thefirst simple planetary gearset PG1 and the ring gear R3 of the thirdsimple planetary gearset PG3. The first clutch C1 is operated in forwardfirst, second and third speeds to connect the planet carrier Ca1 of thefirst simple planetary gearset PG1 to the ring gear R3 of the thirdsimple planetary gearset PG3. A second clutch C2 is interposed betweenthe sun gear S2 of the second simple planetary gearset PG2 and theplanet carrier Ca4 of the fourth simple planetary gearset PG4. Thesecond clutch C2 is operated in forward third, fourth and fifth speedsto connect the sun gear S2 to the planet carrier Ca4.

In addition, a first brake B1 is interposed between the ring gear R3 ofthe third simple planetary gearset PG3 and the transmission housing 20.The first brake B1 is engaged to fix the ring gear R3 in forward firstand fifth speeds and reverse speed. A second brake B2 is interposedbetween the combination of the sun gear S1 and ring gear R2 of the firstand second simple planetary gearsets PG1 and PG2 and the transmissionhousing 20, such that it can operate in the forward second and fourthspeeds and the reverse speed to fix the combination of the sun gear S1and ring gear R2.

The above described geartrain can be illustrated as a leverrepresentation as shown in FIG. 6. In FIG. 6, levers L1 and L2 indicatethe first and second compound planetary gear units 1 and 3,respectively. The four operating elements of the first compoundplanetary gear units 1 are indicated as first, second, third and fourthoperating elements A, D, E and F on the first lever L1, and the fouroperating elements of the second compound planetary gear unit 3 areindicated as first, second, third and fourth operating elements G, H, Iand J on the second lever L2.

In the first lever L1, the first operating element A indicates the sungear S2 of the second simple planetary gearset PG2, the second operatingelement D indicates the planet carrier Ca1 of the first simple planetarygearset PG1, the third operating element E indicates the combination ofthe ring gear R1 and planet Jew carrier Ca2 of the first and secondsimple planetary gearsets PG1 and PG2, and the fourth operating elementF indicates the combination of the sun gear S1 and ring gear R2 of thefirst and second simple planetary gearsets PG1 and PG2.

Since the operating elements of the second lever L2 are the same asthose of the first embodiment, a detailed description thereof will beomitted and incorporated herein as a reference.

The detailed description of shift ratios through the lever analogy willbe omitted herein as the shift ratios are the same as those of the firstembodiment.

Fourth Embodiment

Referring to FIG. 4, there is shown a schematic diagram of a geartrainaccording to a fourth embodiment of the present invention.

The geartrain of this embodiment comprises an engine 100 for generatingpower, a torque converter T for multiplying torque generated from theengine 100, and first and second compound planetary gear units 1 and 3for receiving converted torque through an input shaft 10 and foroutputting five forward speeds and one reverse speed to a transfer drivegear TD.

In this embodiment, the first compound planetary gear unit 1 comprises afirst simple planetary gearset PG1 which is a double pinion planetarygearset and a second simple planetary gearset PG2 which is a singlepinion planetary gearset. The second compound planetary gear unit 3comprises a third simple planetary gearset PG3 which is a double pinionplanetary gearset and a fourth simple planetary gearset PG4 which is asingle pinion planetary gearset.

In the first compound planetary gear unit 1, a sun gear S1 of the firstsimple planetary gearset PG1 is fixedly connected a sun gear S2 of thesecond simple planetary gearset PG2, and a planet carrier Ca1 of thefirst simple planetary gearset PG1 is fixedly connected to a ring gearR2 of the second simple planetary gearset PG2.

Therefore, the first compound planetary gear unit 1 consists of fouroperating elements, i.e., a ring gear R1 of the first simple planetarygearset PG1, a planet carrier Ca2 of the second simple planetary gearsetPG2, a combination of the sun gears S1 and S2 of the first and secondsimple planetary gearsets PG1 and PG2, and a combination of the planetcarrier Ca1 and ring gear R2 of the first and second simple planetarygearsets PG1 and PG2.

Since the structure of the second compound planetary gear unit 3 is thesame as that of the first embodiment, a detailed description thereofwill be omitted and incorporated herein as a reference.

The above described first and second compound planetary gear units 1 and3 are combined to each other. That is, the planet carrier Ca2 of thesecond simple planetary gearset PG2 is fixedly connected to thecombination of the planet carrier Ca3 and sun gear S4 of the third andfourth simple planetary gearsets PG3 and PG4; the ring gear R1 of thefirst simple planetary gearset PG1 is variably connected to the ringgear R3 of the third simple planetary gearset PG3; and the combinationof the sun gears S1 and S2 of the first and second simple planetarygearsets PG1 and PG2 is variably connected to the planet carrier Ca4 ofthe fourth simple planetary gearset PG4. In addition, the combination ofthe sun gear S3 and ring gear R4 of the third and fourth simpleplanetary gearsets PG3 and PG4 is fixed to the transfer drive gear TD.The combination of the sun gears S1 and S2 of the first and secondsimple planetary gearsets PG1 and PG2 is fixed around the input shaft 10so as to act as an input element.

A first clutch C1 is interposed between the ring gear R1 of the firstsimple planetary gearset PG1 and the ring gear R3 of the third simpleplanetary gearset PG3. The first clutch C1 is operated in forward first,second and third speeds to connect the ring gear R1 of the first simpleplanetary gearset PG1 to the ring gear R3 of the third simple planetarygearset PG3. A second clutch C2 is interposed between the combination ofthe sun gears S1 and S2 of the first and second simple planetarygearsets PG1 and PG2 and the planet carrier Ca4 of the fourth simpleplanetary gearset PG4. The second clutch C2 is operated in forwardthird, fourth and fifth speeds to connect the combination of the sungears S1 and S2 to the planet carrier Ca4.

In addition, a first brake B1 is interposed between the ring gear R3 ofthe third simple planetary gearset PG3 and the transmission housing 20.The first brake B1 is engaged to fix the ring gear R3 in forward firstand fifth speeds and reverse speed. A second brake B2 is interposedbetween the combination of the planet carrier Ca1 and ring gear R2 ofthe first and second simple planetary gearsets PG1 and PG2 and thetransmission housing 20, such that it can operate in the forward secondand fourth speeds and the reverse speed to fix the combination of theplanet carrier Ca1 and ring gear R2.

The above described geartrain can be illustrated as a leverrepresentation as shown in FIG. 6. In FIG. 6, levers L1 and L2 indicatethe first and second compound planetary gear units 1 and 3,respectively. The four operating elements of the first compoundplanetary gear units 1 are indicated as first, second, third and fourthoperating elements A, D, E and F on the first lever L1, and the fouroperating elements of the second compound planetary gear unit 3 areindicated as first, second, third and fourth operating elements G, H, Iand J on the second lever L2.

In the first lever L1, the first operating element A indicates thecombination of the sun gears S1 and S2 of the first and second simpleplanetary gearsets PG1 and PG2, the second operating element D indicatesthe ring gear R1 of the first simple planetary gearset PG1, the thirdoperating element E indicates the planet carrier Ca2 of the secondsimple planetary gearset PG2, and the fourth operating element Findicates the combination of the planet carrier Ca1 and ring gear R2 ofthe first and second simple planetary gearsets PG1 and PG2.

Since the operating elements of the second lever L2 are the same asthose of the first embodiment, a detailed description thereof will beomitted and incorporated herein as a reference.

The detailed description of shift ratios through the lever analogy willbe omitted herein as the shift ratios are the same as those of the firstembodiment.

Fifth Embodiment

Referring to FIG. 5, there is shown a schematic diagram of a geartrainaccording to a fifth embodiment of the present invention.

The geartrain of this embodiment comprises an engine 100 for generatingpower, a torque converter T for multiplying torque generated from theengine 100, and first and second compound planetary gear units 1 and 3for receiving converted torque through an input shaft 10 and foroutputting five forward speeds and one reverse speed to a transfer drivegear TD.

In this embodiment, the first compound planetary gear unit 1 comprisesfirst and second simple planetary gearsets PG1 and PG2 each of which isa double pinion planetary gearset. The second compound planetary gearunit 3 comprises a third simple planetary gearset PG3 which is a doublepinion planetary gearset and a fourth simple planetary gearset PG4 whichis a single pinion planetary gearset.

In the first compound planetary gear unit 1, a ring gear R1 of the firstsimple planetary gearset PG1 is fixedly connected a planet carrier Ca2of the second simple planetary gearset PG2, and a planet carrier Ca1 ofthe first simple planetary gearset PG1 is fixedly connected to a sungear S2 of the second simple planetary gearset PG2.

Therefore, the first compound planetary gear unit 1 consists of fouroperating elements, i.e., a sun gear S1 of the first simple planetarygearset PG1, a ring gear R2 of the second simple planetary gearset PG2,a combination of the planet carrier Ca1 and sun gear S2 of the first andsecond simple planetary gearsets PG1 and PG2, and a combination of thering gear R1 and planet carrier Ca2 of the first and second simpleplanetary gearsets PG1 and PG2.

Since the structure of the second compound planetary gear unit 3 is thesame as that of the first embodiment, a detailed description thereofwill be omitted and incorporated herein as a reference.

The above described first and second compound planetary gear units 1 and3 are combined to each other. That is, the ring gear R2 of the secondsimple planetary gearset PG2 is fixedly connected to the combination ofthe planet carrier Ca3 and sun gear S4 of the third and fourth simpleplanetary gearsets PG3 and PG4; the combination of the ring gear R1 andplanet carrier Ca2 of the first and second simple planetary gearsets PG1and PG2 is variably connected to the ring gear R3 of the third simpleplanetary gearset PG3; and the sun gear S1 of the first simple planetarygearset PG1 is variably connected to the planet carrier Ca4 of thefourth simple planetary gearset PG4. In addition, the combination of thesun gear S3 and ring gear R4 of the third and fourth simple planetarygearsets PG3 and PG4 is fixed to the transfer drive gear TD. The sungear S1 of the first simple planetary gearset PG1 is fixed around theinput shaft 10 so as to act as an input element.

A first clutch C1 is interposed between the ring gear R1 of the firstsimple planetary gearset PG1 and the ring gear R3 of the third simpleplanetary gearset PG3. The first clutch C1 is operated in forward first,second and third speeds to connect the ring gear R1 of the first simpleplanetary gearset PG1 to the ring gear R3 of the third simple planetarygearset PG3. A second clutch C2 is interposed between the sun gear S1 ofthe first simple planetary gearset PG1 and the planet carrier Ca4 of thefourth simple planetary gearset PG4. The second clutch C2 is operated inforward third, fourth and fifth speeds to connect the sun gear S1 to theplanet carrier Ca4.

In addition, a first brake B1 is interposed between the ring gear R3 ofthe third simple planetary gearset PG3 and the transmission housing 20.The first brake B1 is engaged to fix the ring gear R3 in forward firstand fifth speeds and reverse speed. A second brake B2 is interposedbetween the combination of the planet carrier Ca1 and sun gear S2 of thefirst and second simple planetary gearsets PG1 and PG2 and thetransmission housing 20, such that it can operate in the forward secondand fourth speeds and the reverse speed to fix the combination of theplanet carrier Ca1 and sun gear S2.

The above described geartrain can be illustrated as a leverrepresentation as shown in FIG. 6. In FIG. 6, levers L1 and L2 indicatethe first and second compound planetary gear units 1 and 3,respectively. The four operating elements of the first compoundplanetary gear units 1 are indicated as first, second, third and fourthoperating elements A, D, E and F on the first lever L1, and the fouroperating elements of the second compound planetary gear unit 3 areindicated as first, second, third and fourth operating elements G, H, Iand J on the second lever L2.

In the first lever L1, the first operating element A indicates the sungear S1 of the first simple planetary gearset PG1, the second operatingelement D indicates the combination of the ring gear R1 and planetcarrier Ca1 of the first and second simple planetary gearsets PG1 andPG2, the third operating element E indicates the ring gear R2 of thesecond simple planetary gearset PG2, and the fourth operating element Findicates the combination of the planet carrier Ca1 and sun gear S2 ofthe first and second simple planetary gearsets PG1 and PG2.

Since the operating elements of the second lever L2 are the same asthose of the first embodiment, a detailed description thereof will beomitted and incorporated herein as a reference.

The detailed description of shift ratios through the lever analogy willbe omitted herein as the shift ratios are the same as those of the firstembodiment.

In this disclosure, there is shown and described only the preferredembodiments of the invention, as aforementioned, it is to be understoodthat the invention is capable of use in various other combinations andenvironments and is capable of change or modification within the scopeof the inventive concepts as expressed herein.

What is claimed is:
 1. A geartrain for a five-speed automatictransmission, comprising:a first compound planetary gear unit comprisingfirst and second simple planetary gearsets having first, second, thirdand fourth operating elements, said first operating element acting as aninput element; a second compound planetary gear unit comprising thirdand fourth simple planetary gearsets having fifth, sixth, seventh andeighth operating elements, said fifth operating element acting as anoutput element, said sixth and seventh operating elements being variablyconnected to said first and second operating elements, respectively, andsaid eighth operating element being fixedly connected to the thirdoperating element; clutch means for variably connecting said sixth andseventh operating elements to said first and second operating elements,respectively; and brake means for selectively connecting the fourth andseventh operating elements to a transmission housing.
 2. A geartrain ofclaim 1, wherein each of said first and second simple planetary gearsetsis a single pinion planetary gearset.
 3. A geartrain of claim 2, whereinthe first operating element is a sun gear of the first simple planetarygearset;the second operating element is a ring gear of the second simpleplanetary gearset; the third operating element is a combination of aplanet carrier of the first simple planetary gearset and a planetcarrier of the second simple planetary gearset; and the fourth operatingelement is a combination of a ring gear of the first simple planetarygearset and a sun gear of the second simple planetary gearset.
 4. Ageartrain of claim 3, wherein the third simple planetary gearset is adouble pinion planetary gearset, and the fourth simple planetary gearsetis a single pinion planetary gearset.
 5. A geartrain of claim 4, whereinthe fifth operating element is a combination of a sun gear of the thirdsimple planetary gearset and a ring gear of the fourth simple planetarygearset;the sixth operating element is a planet carrier of the fourthsimple planetary gearset; the seventh operating element is a ring gearof the third simple planetary gearset; and the eighth operating elementis a combination of a planet carrier of the third simple planetarygearset and a sun gear of the fourth simple planetary gearset.
 6. Ageartrain of claim 5, wherein the clutch means comprises a first clutchinterposed between the ring gear of the second simple planetary gearsetand the ring gear of the third simple planetary gearset and a secondclutch interposed between the sun gear of the first simple planetarygearset and the planet carrier of the fourth simple planetary gearset.7. A geartrain of claim 5, wherein the brake means comprises a firstbrake interposed between the ring gear of the third simple planetarygearset and the transmission housing and a second brake interposedbetween the combination of the ring gear of the first simple planetarygearset and the sun gear of the second simple planetary gearset and thetransmission housing.
 8. A geartrain of claim 1, wherein the firstsimple planetary gearset is a double pinion planetary gearset, and thesecond simple planetary gearset is a single pinion planetary gearset. 9.A geartrain of claim 8, wherein the first operating element is a sungear of the first simple planetary gearset;the second operating elementis a combination of a ring gear of the first simple planetary gearsetand a ring gear of the second simple planetary gearset; the thirdoperating element is a planet carrier of the second simple planetarygearset; and the fourth operating element is a combination of a planetcarrier of the first simple planetary gearset and a sun gear of thesecond simple planetary gearset.
 10. A geartrain of claim 9, wherein thethird simple planetary gearset is a double pinion planetary gearset andthe fourth simple planetary gearset is a single pinion planetarygearset.
 11. A geartrain of claim 10, wherein the fifth operatingelement is a combination of a sun gear of the third simple planetarygearset and a ring gear of the fourth simple planetary gearset;the sixthoperating element is a planet carrier of the fourth simple planetarygearset; the seventh operating element is a ring gear of the thirdsimple planetary gearset; and the eighth operating element is acombination of a planet carrier of the third simple planetary gearsetand a sun gear of the fourth simple planetary gearset.
 12. A geartrainof claim 11, wherein the clutch means comprises a first clutchinterposed between the combination of the ring gear of the first simpleplanetary gearset and the ring gear of the second simple planetarygearset and the ring gear of the third simple planetary gearset, and asecond clutch interposed between the sun gear of the first simpleplanetary gearset and the planet carrier of the fourth simple planetarygearset.
 13. A geartrain of claim 11, wherein the brake means comprisesa first brake interposed between the ring gear of the third simpleplanetary gearset and the transmission housing and a second brakeinterposed between the combination of the planet carrier of the firstsimple planetary gearset and the sun gear of the second simple planetarygearset and the transmission housing.
 14. A geartrain of claim 8,wherein the first operating element is a sun gear of the second simpleplanetary gearset;the second operating element is a planet carrier ofthe first simple planetary gearset; the third operating element is acombination of a ring gear of the first simple planetary gearset and aplanet carrier of the second simple planetary gearset; and the fourthoperating element is a combination of a sun gear of the first simpleplanetary gearset and a ring gear of the second simple planetarygearset.
 15. A geartrain of claim 14, wherein the third simple planetarygearset is a double pinion planetary gearset and the fourth simpleplanetary gearset is a single pinion planetary gearset.
 16. A geartrainof claim 15, wherein the fifth operating element is a combination of asun gear of the third simple planetary gearset and a ring gear of thefourth simple planetary gearset;the sixth operating element is a planetcarrier of the fourth simple planetary gearset; the seventh operatingelement is a ring gear of the third simple planetary gearset; and theeighth operating element is a combination of a planet carrier of thethird simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.
 17. A geartrain of claim 16, wherein the clutch meanscomprises a first clutch interposed between the planet carrier of thefirst simple planetary gearset and the ring gear of the third simpleplanetary gearset, and a second clutch interposed between the sun gearof the second simple planetary gearset and the planet carrier of thefourth simple planetary gearset.
 18. A geartrain of claim 16, whereinthe brake means comprises a first brake interposed between the ring gearof the third simple planetary gearset and the transmission housing, anda second brake interposed between the combination of the sun gear of thefirst simple planetary gearset and the ring gear of the second simpleplanetary gearset and the transmission housing.
 19. A geartrain of claim8, wherein the first operating element is a combination of a sun gear ofthe first simple planetary gearset and a sun gear of the second simpleplanetary gearset;the second operating element is a ring gear of thefirst simple planetary gearset; the third operating element is a planetcarrier of the second simple planetary gearset; and the fourth operatingelement is a combination of a planet carrier of the first simpleplanetary gearset and a ring gear of the second simple planetarygearset.
 20. A geartrain of claim 19, wherein the third simple planetarygearset is a double pinion planetary gearset and the fourth simpleplanetary gearset is a single pinion planetary gearset.
 21. A geartrainof claim 20, wherein the fifth operating element is a combination of asun gear of the third simple planetary gearset and a ring gear of thefourth simple planetary gearset;the sixth operating element is a planetcarrier of the fourth simple planetary gearset; the seventh operatingelement is a ring gear of the third simple planetary gearset; and theeighth operating element is a combination of a planet carrier of thethird simple planetary gearset and a sun gear of the fourth simpleplanetary gearset.
 22. A geartrain of claim 21, wherein the clutch meanscomprises a first clutch interposed between the ring gear of the firstsimple planetary gearset and the ring gear of the third simple planetarygearset, and a second clutch interposed between the combination of thesun gear of the first simple planetary gearset and the sun gear of thesecond simple planetary gearset and the planet carrier of the fourthsimple planetary gearset.
 23. A geartrain of claim 21, wherein the brakemeans comprises a first brake interposed between the ring gear of thethird simple planetary gearset and the transmission housing, and asecond brake interposed between the combination of the planet carrier ofthe third simple planetary gearset and the ring gear of the secondsimple planetary gearset and the transmission housing.
 24. A geartrainof claim 1, wherein each of the first and second simple planetarygearsets is a double pinion planetary gearset.
 25. A geartrain of claim24, wherein the first operating element is a sun gear of the firstsimple planetary gearset;the second operating element is a combinationof a ring gear of the first simple planetary gearset and a planetcarrier of the second simple planetary gearset; the third operatingelement is a ring gear of the second simple planetary gearset; and thefourth operating element is a combination of a planet carrier of thefirst simple planetary gearset and a sun gear of the second simpleplanetary gearset.
 26. A geartrain of claim 25, wherein the third simpleplanetary gearset is a double pinion planetary gearset and the fourthsimple planetary gearset is a single pinion planetary gearset.
 27. Ageartrain of claim 25, wherein the fifth operating element is acombination of a sun gear of the third simple planetary gearset and aring gear of the fourth simple planetary gearset;the sixth operatingelement is a planet carrier of the fourth simple planetary gearset; theseventh operating element is a ring gear of the third simple planetarygearset; and the eighth operating element is a combination of a planetcarrier of the third simple planetary gearset and a sun gear of thefourth simple planetary gearset.
 28. A geartrain of claim 27, whereinthe clutch means comprises a first clutch interposed between thecombination of the ring gear of the first simple planetary gearset andthe planet carrier of the second simple planetary gearset and the ringgear of the third simple planetary gearset, and a second clutchinterposed between the sun gear of the first simple planetary gearsetand the planet carrier of the fourth simple planetary gearset.
 29. Ageartrain of claim 27, wherein the brake means comprises a first brakeinterposed between the ring gear of the third simple planetary gearsetand the transmission housing, and a second brake interposed between thecombination of the planet carrier of the first simple planetary gearsetand the sun gear of the second simple planetary gearset and thetransmission housing.